Adriaan Daniël Fokker (; 17 August 1887 – 24 September 1972) was a Dutch

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...

. He worked in the fields of

special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates: # The laws o ...

and

statistical mechanics In physics, statistical mechanics is a mathematical framework that applies statistical methods and probability theory to large assemblies of microscopic entities. It does not assume or postulate any natural laws, but explains the macroscopic be ...

. He was the inventor of the Fokker organ, a 31-tone equal-tempered (31-TET) organ.

Life and work

Adriaan Daniël Fokker was born on 17 August 1887 in Buitenzorg,

Dutch East Indies The Dutch East Indies, also known as the Netherlands East Indies ( nl, Nederlands(ch)-Indië; ), was a Dutch colony consisting of what is now Indonesia. It was formed from the nationalised trading posts of the Dutch East India Company, which ...

(now

Bogor Bogor ( su, , nl, Buitenzorg) is a city in the West Java province, Indonesia. Located around south of the national capital of Jakarta, Bogor is the 6th largest city in the Jakarta metropolitan area and the 14th overall nationwide.Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

). He was a cousin of the

aeronautical Aeronautics is the science or art involved with the study, design, and manufacturing of air flight–capable machines, and the techniques of operating aircraft and rockets within the atmosphere. The British Royal Aeronautical Society identifies ...

engineer Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the l ...

Anthony Fokker Anton Herman Gerard "Anthony" Fokker (6 April 1890 – 23 December 1939) was a Dutch aviation pioneer, aviation entrepreneur, aircraft designer, and aircraft manufacturer. He produced fighter aircraft in Germany during the First World War such ...

. Fokker studied

mining engineering Mining in the engineering discipline is the extraction of minerals from underneath, open pit, above or on the ground. Mining engineering is associated with many other disciplines, such as mineral processing, exploration, excavation, geology, and ...

at the

Delft University of Technology Delft University of Technology ( nl, Technische Universiteit Delft), also known as TU Delft, is the oldest and largest Dutch public technical university, located in Delft, Netherlands. As of 2022 it is ranked by QS World University Rankings among ...

and

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

at the

University of Leiden Leiden University (abbreviated as ''LEI''; nl, Universiteit Leiden) is a public research university in Leiden, Netherlands. The university was founded as a Protestant university in 1575 by William, Prince of Orange, as a reward to the city of Le ...

with

Hendrik Lorentz Hendrik Antoon Lorentz (; 18 July 1853 – 4 February 1928) was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect. He also derived the Lorentz t ...

, where he earned his

doctorate A doctorate (from Latin ''docere'', "to teach"), doctor's degree (from Latin ''doctor'', "teacher"), or doctoral degree is an academic degree awarded by universities and some other educational institutions, derived from the ancient formalism ''l ...

in 1913. He continued his studies with

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics. ''Encyclopædia Britannica'' considers him to be the greatest ...

and William Bragg. In his 1913 thesis, he derived the

Fokker–Planck equation In statistical mechanics, the Fokker–Planck equation is a partial differential equation that describes the time evolution of the probability density function of the velocity of a particle under the influence of drag forces and random forces, as ...

along with

Max Planck Max Karl Ernst Ludwig Planck (, ; 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical p ...

. After his

military service Military service is service by an individual or group in an army or other militia, air forces, and naval forces, whether as a chosen job (volunteer) or as a result of an involuntary draft (conscription). Some nations (e.g., Mexico) require a ...

during

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

he returned to

Leiden Leiden (; in English and archaic Dutch also Leyden) is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden has a population of 119,713, but the city forms one densely connected agglomeration wit ...

as Lorentz' and

Ehrenfest Ehrenfest is a surname. Notable people with the surname include: *Paul Ehrenfest (1880-1933), Austrian physicist and mathematician **Ehrenfest equations **Ehrenfest model **Ehrenfest paradox **Ehrenfest theorem The Ehrenfest theorem, named after P ...

's assistant. Fokker became a physics teacher at the Gymnasium of Delft after 1918 and was appointed in 1923 as the first professor of Applied Physics at the Technische Hoogeschool Delft (today Delft University of Technology). In 1928 Fokker succeeded

as director of research at

Teylers Museum Teylers Museum () is an art, natural history, and science museum in Haarlem, Netherlands. Established in 1778, Teylers Museum was founded as a centre for contemporary art and science. The historic centre of the museum is the neoclassical Oval R ...

Haarlem Haarlem (; predecessor of ''Harlem'' in English) is a city and municipality in the Netherlands. It is the capital of the province of North Holland. Haarlem is situated at the northern edge of the Randstad, one of the most populated metropoli ...

. Fokker made several contributions to

, and some less well-known contributions to

general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...

, particularly in the area of geodetic precession, the phenomena of precession of a freely falling gyroscope in a gravitational field. Fokker began to study

music theory Music theory is the study of the practices and possibilities of music. ''The Oxford Companion to Music'' describes three interrelated uses of the term "music theory". The first is the "rudiments", that are needed to understand music notation (ke ...

during the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, when the University of Leiden was closed; partly this was due to a desire to convince the

Nazis Nazism ( ; german: Nazismus), the common name in English for National Socialism (german: Nationalsozialismus, ), is the far-right totalitarian political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in Na ...

he would be of no use to the war effort, and partly it was a response to reading the work of

Christiaan Huygens Christiaan Huygens, Lord of Zeelhem, ( , , ; also spelled Huyghens; la, Hugenius; 14 April 1629 – 8 July 1695) was a Dutch mathematician, physicist, engineer, astronomer, and inventor, who is regarded as one of the greatest scientists of ...

on the

31 equal temperament In music, 31 equal temperament, 31-ET, which can also be abbreviated 31-TET (31 tone ET) or 31- EDO (equal division of the octave), also known as tricesimoprimal, is the tempered scale derived by dividing the octave into 31 equal-sized steps (equ ...

. In 1938, Fokker – along with

Dirk Coster Dirk Coster (October 5, 1889 – February 12, 1950), was a Dutch physicist. He was a Professor of Physics and Meteorology at the University of Groningen. Coster was born in Amsterdam. On February 26, 1919, he married Lina Maria Wijsman, who ...

and

Otto Hahn Otto Hahn (; 8 March 1879 – 28 July 1968) was a German chemist who was a pioneer in the fields of radioactivity and radiochemistry. He is referred to as the father of nuclear chemistry and father of nuclear fission. Hahn and Lise Meitner ...

– helped Jewish-born physicist

Lise Meitner Elise Meitner ( , ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish physicist who was one of those responsible for the discovery of the element protactinium and nuclear fission. While working at the Kaiser Wilhelm Institute on rad ...

escape from Austria to the Netherlands. "Fokker and Coster both knew that university positions were virtually unavailable for foreigners. Laboratory space was not a problem, however, either in Groningen or Haarlem. 'Perhaps we can tap colleagues for regular contributions,' Coster suggested. Fokker set a goal of f.20,000, enough to support Meitner for five years, and immediately began contacting colleagues for advice and donations." They were unsuccessful in obtaining funding, but Fokker succeeded in getting official permission for Meitner to leave, although he was unable to telegraph that to her due to secrecy. She escaped barely in time to evade arrest. The year 1942 consequently marked a turning point in his life; after then he wrote many pieces in 31-equal, which are notable for using the 7th

harmonic A harmonic is a wave with a frequency that is a positive integer multiple of the ''fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', the ...

as a consonant interval (31-equal has a much better approximation of the 7th harmonic than the ubiquitous 12-equal). He also made notable contributions to music theory, such as the Fokker periodicity block. In 1949 he became member of the

Royal Netherlands Academy of Arts and Sciences The Royal Netherlands Academy of Arts and Sciences ( nl, Koninklijke Nederlandse Akademie van Wetenschappen, abbreviated: KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed ...

. He died on 24 September 1972, at the age of 85, in

Beekbergen Beekbergen (; nds, Bekbargen or ''Beekbargen'') is a village and former municipality in the Dutch province of Gelderland. It is located in the municipality of Apeldoorn on the edge of the Veluwe. The rural area on the southwestern side of the v ...

near

Apeldoorn Apeldoorn (; Dutch Low Saxon: ) is a municipality and city in the province of Gelderland in the centre of the Netherlands. It is located about 60 km east of Utrecht, 60 km west of Enschede, 25 km north of Arnhem and 35 km south of Zwolle. The ...

Musical instruments

Fokker designed and had built a number of keyboard instruments capable of playing microtonal scales via a

generalized keyboard Generalized keyboards are musical Keyboard (music), keyboards, a type of isomorphic keyboard, with regular, tile-like arrangements usually with rectangular or hexagonal keys, and were developed for performing music in different Tuning (music), tuni ...

. The best-known of these is his 31-tone equal-tempered organ, which was installed in Teyler's Museum in Haarlem in 1951. It is commonly called the Fokker organ. The Fokker organ is currently property of the

Huygens-Fokker Foundation The Huygens-Fokker Foundation () is a "centre for microtonal music" founded on February 15, 1960, housed in the Muziekgebouw aan 't IJ (Amsterdam, Netherlands), and named for Christiaan Huygens and Adriaan Fokker (inventor of 31 equal temperament ...

and it moved to the Bamzaal in

Muziekgebouw aan 't IJ Muziekgebouw aan 't IJ (English language, English: "Music Building on the IJ") is the main concert hall for contemporary classical music on the IJ (Amsterdam), IJ in Amsterdam, Netherlands. The building opened in 2005 and is located above the IJt ...

. Regularly concerts take place on this instrument in the Bamzaal.

References and notes

External links

Oral history interview transcript with Adriaan Fokker on 1 April 1963, American Institute of Physics, Niels Bohr Library & Archives

Adriaan Fokker and the Archiphone on '120 Years Of Electronic Music'
from the Huygens–Fokker Foundation * H.A.M. Snelders,
Fokker, Adriaan Daniël (1887–1972)
, in Biografisch Woordenboek van Nederland. 3-03-2008 {{DEFAULTSORT:Fokker, Adriaan 1887 births 1972 deaths 20th-century Dutch physicists 20th-century Dutch inventors Microtonal musicians Dutch music theorists Delft University of Technology alumni Leiden University alumni People from Bogor Musicians from West Java Members of the Royal Netherlands Academy of Arts and Sciences Members of Teylers Tweede Genootschap 20th-century musicologists Dutch people of the Dutch East Indies

Life and work

Musical instruments

See also

References and notes

External links